Re: About locks and concurrency rules for SMP systems

2021-03-29 Thread Richi Dubey 
Got it. Thank you for the clarification.

On Fri, Mar 26, 2021 at 8:32 PM Gedare Bloom  wrote:

> On Thu, Mar 25, 2021 at 11:30 PM Richi Dubey  wrote:
> >
> > Thanks for your quick response!
> >
> >> Each scheduler has its own lock. There are a couple of more locks
> involved.
> >
> > I understand.
> >
> > I backtracked a little and found that we have:
> > _Thread_State_acquire_critical( the_thread, lock_context );
> >
> > to lock access to thread-specific variables.
> >
> > _Scheduler_Acquire_critical( scheduler, _context
> >
> > to lock access to the current scheduler-specific data structures.
> >
> > What other locks do we have related to schedulers?
> >
>
> By definition, all locks relate to scheduling. The other major one
> though would be _Thread_Dispatch_disable_critical and relatives like
> _Thread_queue_Dispatch_disable, if you think of dispatching as part of
> scheduling. However, the two operations are a little bit different.
> Scheduling is selecting the next thread(s) to run, while dispatching
> is actually making them run.
>
>
> > On Wed, Mar 24, 2021 at 1:03 PM Sebastian Huber <
> sebastian.hu...@embedded-brains.de> wrote:
> >>
> >> On 24/03/2021 08:07, Richi Dubey wrote:
> >>
> >> > How does RTEMS handle cases where two different cores access
> >> > scheduler-related functions at the same time?
> >> Each scheduler has its own lock. There are a couple of more locks
> involved.
> >> > For ex., Can they access (or modify) the Scheduler_strong_APA_Context
> >> > <
> https://git.rtems.org/rtems/tree/cpukit/include/rtems/score/schedulerstrongapa.h#n61
> >
> >> > at the same time?
> >> No, unless we have a bug.
> >>
> >> --
> >> embedded brains GmbH
> >> Herr Sebastian HUBER
> >> Dornierstr. 4
> >> 82178 Puchheim
> >> Germany
> >> email: sebastian.hu...@embedded-brains.de
> >> phone: +49-89-18 94 741 - 16
> >> fax:   +49-89-18 94 741 - 08
> >>
> >> Registergericht: Amtsgericht München
> >> Registernummer: HRB 157899
> >> Vertretungsberechtigte Geschäftsführer: Peter Rasmussen, Thomas Dörfler
> >> Unsere Datenschutzerklärung finden Sie hier:
> >> https://embedded-brains.de/datenschutzerklaerung/
> >>
> > ___
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>
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Re: About locks and concurrency rules for SMP systems

2021-03-26 Thread Gedare Bloom 
On Thu, Mar 25, 2021 at 11:30 PM Richi Dubey  wrote:
>
> Thanks for your quick response!
>
>> Each scheduler has its own lock. There are a couple of more locks involved.
>
> I understand.
>
> I backtracked a little and found that we have:
> _Thread_State_acquire_critical( the_thread, lock_context );
>
> to lock access to thread-specific variables.
>
> _Scheduler_Acquire_critical( scheduler, _context
>
> to lock access to the current scheduler-specific data structures.
>
> What other locks do we have related to schedulers?
>

By definition, all locks relate to scheduling. The other major one
though would be _Thread_Dispatch_disable_critical and relatives like
_Thread_queue_Dispatch_disable, if you think of dispatching as part of
scheduling. However, the two operations are a little bit different.
Scheduling is selecting the next thread(s) to run, while dispatching
is actually making them run.


> On Wed, Mar 24, 2021 at 1:03 PM Sebastian Huber 
>  wrote:
>>
>> On 24/03/2021 08:07, Richi Dubey wrote:
>>
>> > How does RTEMS handle cases where two different cores access
>> > scheduler-related functions at the same time?
>> Each scheduler has its own lock. There are a couple of more locks involved.
>> > For ex., Can they access (or modify) the Scheduler_strong_APA_Context
>> > 
>> > at the same time?
>> No, unless we have a bug.
>>
>> --
>> embedded brains GmbH
>> Herr Sebastian HUBER
>> Dornierstr. 4
>> 82178 Puchheim
>> Germany
>> email: sebastian.hu...@embedded-brains.de
>> phone: +49-89-18 94 741 - 16
>> fax:   +49-89-18 94 741 - 08
>>
>> Registergericht: Amtsgericht München
>> Registernummer: HRB 157899
>> Vertretungsberechtigte Geschäftsführer: Peter Rasmussen, Thomas Dörfler
>> Unsere Datenschutzerklärung finden Sie hier:
>> https://embedded-brains.de/datenschutzerklaerung/
>>
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Re: About locks and concurrency rules for SMP systems

2021-03-25 Thread Richi Dubey 
Thanks for your quick response!

Each scheduler has its own lock. There are a couple of more locks involved.

I understand.

I backtracked a little and found that we have:
_Thread_State_acquire_critical( the_thread, lock_context );

to lock access to thread-specific variables.

_Scheduler_Acquire_critical( scheduler, _context );

to lock access to the current scheduler-specific data structures.

What other locks do we have related to schedulers?

On Wed, Mar 24, 2021 at 1:03 PM Sebastian Huber <
sebastian.hu...@embedded-brains.de> wrote:

> On 24/03/2021 08:07, Richi Dubey wrote:
>
> > How does RTEMS handle cases where two different cores access
> > scheduler-related functions at the same time?
> Each scheduler has its own lock. There are a couple of more locks involved.
> > For ex., Can they access (or modify) the Scheduler_strong_APA_Context
> > <
> https://git.rtems.org/rtems/tree/cpukit/include/rtems/score/schedulerstrongapa.h#n61>
>
> > at the same time?
> No, unless we have a bug.
>
> --
> embedded brains GmbH
> Herr Sebastian HUBER
> Dornierstr. 4
> 82178 Puchheim
> Germany
> email: sebastian.hu...@embedded-brains.de
> phone: +49-89-18 94 741 - 16
> fax:   +49-89-18 94 741 - 08
>
> Registergericht: Amtsgericht München
> Registernummer: HRB 157899
> Vertretungsberechtigte Geschäftsführer: Peter Rasmussen, Thomas Dörfler
> Unsere Datenschutzerklärung finden Sie hier:
> https://embedded-brains.de/datenschutzerklaerung/
>
>
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Re: About locks and concurrency rules for SMP systems

2021-03-24 Thread Sebastian Huber 

On 24/03/2021 08:07, Richi Dubey wrote:

How does RTEMS handle cases where two different cores access 
scheduler-related functions at the same time? 

Each scheduler has its own lock. There are a couple of more locks involved.
For ex., Can they access (or modify) the Scheduler_strong_APA_Context 
 
at the same time?

No, unless we have a bug.

--
embedded brains GmbH
Herr Sebastian HUBER
Dornierstr. 4
82178 Puchheim
Germany
email: sebastian.hu...@embedded-brains.de
phone: +49-89-18 94 741 - 16
fax:   +49-89-18 94 741 - 08

Registergericht: Amtsgericht München
Registernummer: HRB 157899
Vertretungsberechtigte Geschäftsführer: Peter Rasmussen, Thomas Dörfler
Unsere Datenschutzerklärung finden Sie hier:
https://embedded-brains.de/datenschutzerklaerung/

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About locks and concurrency rules for SMP systems

2021-03-24 Thread Richi Dubey 
Hi,

How does RTEMS handle cases where two different cores access
scheduler-related functions at the same time? For ex., Can they access (or
modify) the Scheduler_strong_APA_Context

at the same time?

Thanks
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